The invention relates to a method for producing Ph.sub.3 C[B(C.sub.6 F.sub.5).sub.4 ]. The "cation" of the compound [Et(Ind).sub.2 Zr(CH.sub.3)].sup.+ B(C.sub.6 F.sub.5).sub.4.sup.- (Ind=Indenyl) is a catalyst for the isospecific polymerization of propylene. The catalytic compound is produced in accordance with the following reaction equation: EQU Et(Ind).sub.2 Zr(CH.sub.3).sub.2 +Ph.sub.3 C[B(C.sub.6 F.sub.5).sub.4 ]-.fwdarw.[Et(Ind).sub.2 Zr(CH.sub.3)].sup.+ B(C.sub.6 F.sub.5).sub.4.sup.- +Ph.sub.3 CCH.sub.3.
The Ph.sub.3 C[B(C.sub.6 F.sub.5).sub.4 ] which is required as an intermediate product, and its production are described by J. C. W. Chien, Woei-Min Tsai and M. D. Rausch in J. Am. Chem. Soc. 113 (1991), pages 8570 and 8571. In the method described therein, LiB(C.sub.6 F.sub.5).sub.4 is mixed under an argon atmosphere with triphenylmethyl chloride (Ph.sub.3 CCl) in 200 ml dry n-hexane and is refluxed overnight. The yellow solid was dissolved in dichloromethane and lithium chloride was removed by filtration. The product was then recrystallized from dichloromethane/hexane, and was obtained in the form of orange-colored crystals. The yield is given as 64%.